Electronic trigger circuit with pulse output attenuating means



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A. H. Dl'CKlNSON ELECTRONIC TRIGGER CIRCUIT WITH PULSE OUTPUT ATTENUATING MEANS Original Filed Dec. 27, 1945 ENQ@ IMM x w. m @wi All a. Wm.

@ggg m Patented Dec. 21, 1948 ZASbld ELECTRONIC TRIGGER CIRCUIT WITH PULSE OUTPUT ATTENUATING MEANS Arthur H. Dickinson, Greenwich, Conn., assigner to International Business Machines Corporation, New York, N. Y., a corporation of New York Original application December 27, 1943, Serial No. 5145,719. Divided and this application March 17, i945, Serial No. 583,273

(Cl. Z50- 27) 2 Claims. 1

This application is a division of my application Serial No. 515,719, led December 27, 1943, and is directed to improvements in electronic switching arrangements.

The electronic switching means with which the invention is concerned comprises electronic trigger circuits. This trigger circuit may assume either of two opposite electrical conditions. rIhe circuit is so biased that upon application of a pulse of sufcient amplitude to a point of the circuit, it will be tripped to a reverse condition. If the pulse impressed on this point of the circuit be positive and of adequate value, it will be capable of tripping the circuit from one of its conditions to the reverse condition. If the pulse impressed on the same point of the circuit be negative and oi sufcient value, it will be capable of tripping the circuit from said reverse condition to the alternate condition. As a trigger circuit is tripped from one condition to the other, positive and negative pulses may be derived therefrom. A particular point of this circuit will provide a positive pulse when the circuit is tripped to one state and a negative pulse when the circuit is returned to its previous state. If this point of the circuit be coupled directly to a point of another such trigger circuit, a double reversal or reciprocation in status of the first circuit may eiect a double reversal on reciprocation in status of the second circuit. It is desirable, however, in many cases, to trip the second circuit only in one direction for each reciprocation in status of the first circuit. For this purpose, the prior art has provided electronic discharge means between the first and second circuits.

An object of the present invention is to provide trigger circuits of such nature that a controlling trigger circuit may be coupled to a controlled trigger circuit without intervening electronic discharge means and yet, upon a reciprocation in status, efiect only a single reversal of the controlled trigger circuit.

An object of the invention is to provide an electronic trigger circuit which upon a reciprocation in its status will produce positive and negative pulses of unequal amplitude in combination with means for applying these pulses with selective or discriminative effect upon a controlled circuit.

An object of the invention is to provide electronic trigger circuits, one of which may be coupled without intervening electronic discharge means to a point of a controlled trigger circuit, and which will act with discriminative effe-ct upon the point of the controlled trigger circuit.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle oi the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a circuit diagram of elements involved in the invention.

Fig. 2 is a diagrammatic showing of the waves of potential produced at pertinent points of the circuit network shown in Fig. 1.

Referring to Fig. l, a line switch. i536 is closed to connect a suitable source of potential to lines 54 and 5I. Across these lines is a voltage divider btw-5% tapped by lines 50, 6l, and Sil which are positive with respect'to each other and to line 5l in the order named.

Pulses are required for operating elements ci the apparatus, Preferably, an oscillator of the multivibrator type is used as the main source of pulses. The multivibrator produces two trains of square-topped pulses, each train being 180 degrees out of phase with the other. Such pulses are suitable for conversion into derived pulses of extremely steep wave front and short duration.

In Fig. 1, the multivibrator oscillator, as a Whole, is designated M. It includes two triodes 83a and 83h which are shown, for convenience, as units of a duplex tube. The common cathode of the triodes vis connected to line 6I. The individual anodes are connected by resistors 84a and 84h to line 50. The grid of 33a is coupled by a condenser 85a to the anode of triode 83h, while the grid of 83h is coupled by a condenser 85h to the anode of 83a. Grid lead resistances tta and @b connect the condensers and associated grids to line El. The operation of the multivibrator is well-known and it is sufficient to state that square-topped pulses of potential are produced on the anode of 33a which are 180 degrees shifted in phase with respect to similar pulses on the anode of 83h. For the present case, only those pulses on the anode of 83a are used. The form of these pulses is indicated in Fig. 2.

The rise and fall of potential on the anode of S3 are communicated by a condenser 88am to a resistor SSaaa. The R. C. produ-ct of this condenser and resistor is relatively small so that the square-topped pulses on the anode of 83a are transformed into very sharp pulses on resistor 890mg, as indicated in Fig. 2. Resistor BSaaa is tappedby the grid of a triode Sliema. The cathode of this triode is connected to line 5l and its anode is connected by a resistor Slaaa to line 50. The

triode 90am is of the type which is fully conductive when it is at zero grid bias. Since the cathode of the triode and the resistor 85aaa both connect .to line Bi, the triode is normally at zero grid bias and is fully conductive. Accordingly, the positive pulses fed to the grid of triode Stada from resistor ilaaa have no appreciable elect. On the other hand, the negative pulses received from 89am by the grid of Silaaa so reduce the grid potential as to drive Silaaa to cut-off. Each time the triode is driven to cut-off, an amplified posi.- tive puse appears at the lower end of resistor giada, as indicated in Fig. 2.

The resistor 9 laad is connected by a condenser |23 to a resistor |29 which is tapped by the suppressor of a pentode tube |3'D. Hence, the positive pulses on resistor 9|aaa willproduce corresponding positive potential pulses on the supu pressor of the tube |30. The screen of this tube is maintained at suitable iiXed potential by connection to the junction of resistors |3| and 32 and by a condenser |33 which shunts |32. The control grid of tube I3@ is connected to a point y3`|L of a trigger circuit I which ,will be described later. Point i'lL may be at either of relatively high and low potentials. When point lL is at its high potential, the control grid bias of tube |39 is substantially zero, whereby the tube will become conductive each time -a positive pulse is fed to its suppressor from the resistor |29. When point S'IL is at lower potential, the tube |30 is maintained at cut-off even at the time a positive pulse appears on the suppressor. The resistor |29, to which the suppressor is connected, terminates at line 5| which is lower in potential than line 6| to which is connected the cathode of tube |30. The relation is such that in the absence of a positive pulse on the resistor |29, the suppressor potential will be sufliciently less than cathode potential to prevent appreciable current flow even when the control grid bias is zero. When the control grid bias is zero, the positive pulses fed "to the suppressor will be converted by tube |39 into negative pulses on anoderesistor |34 andconnected wire 20. The form of these negative pulses on wire |243 is shown in Fig. 2. When the control grid bias is at cut-off, then the positive pulses on the suppressor will be ineffective, and negative pulses will not be produced by the tube |39, which accounts for the absence of some of these pulses in Fig. 2. The purpose ci these negative pulses will be made clear later.

The trigger circuit will now be described. There are two similar trigger circuits shown in Fig. l, One of these is designated I and the other is designated E. Since both trigger circuits are alike, it will be sufficient to explain circuit I in detail.

The trigger circuit comprises two impedance networks which may be referred to as left and right hand sides or impedance branches. The branches are symmetrical and `corresponding elements have the same electrical value and are given the same reference number which may be accompanied by letter L or R to denote left .or right hand side, respectively. Each impedance branch comprises resistors 62, 63, and 54, which constitute a voltage divider, a triode B8, and a vcondenser 65 shunting resistor 6.3. The triodes 58L and 63B, are shown as units of a duplex tube,

for convenience. The grid of the triode in each branch connects to the point 6] of the opposite branch. The two impedance branches are thus cross-coupled. The anode of each triode connects to line 5|) via the related resistor 62. The common cathode .of the triode connects to line siii gli.

4 6|. An efficient arrangement of the circuit is one in which resistors 62 and 64 are equal in value, resistors E3 are approximately three times this value, and condensers 65 have a capacity of the order of a few hundred micromicrofarads.

The two impedance branches of the trigger cir- .cuit are so interconnected that when one branch is at low impedance (its triode conducting), the other branch is at high impedance (its triode non-conducting) Assume that the left branch is .at low impedance; i. e., its triode GSL is conductive. Accordingly, point iGL is only slightly above cathode potential and the potential drop across resistors 63L and iL forces the potential at point EVIL below that of cathode line 6l Since the grid of triode GBR is connected to point e'lL, then SBR will be held at such negative grid bias as to be at cut-o. Hence, the point GSR will be at high potential, and the drop across resistors 631., and MR does not force the potential at point 61H to cuto value. Since point SlR is connected to the grid of triode GBL the triode will then .be maintained conductive status. The above conditions define one stable state cf the kcircuit which may be termed, for convenience. the on state.

The reverse or off stateA is one in which .triode SBR is conductive and triode BBL is non-.conductive. The interaction between the branches is such that, for reasons already made clear, the circuit is self-sustaining in either status. Aglow discharge tube Eli is connected via a resistor iid to point SGL of the trigger circuit. When the circuit is in on state, point L is at low potential, and there is sufficient .potential drop across the tube 13 to light the tube. But, when the circuit is ofi, then point SSL is at high potential, and tube 'i8 remains unlit. Thus, tube l?, when lit, indicates that the trigger circuit is on. To reverse the status of the circuit, an electrical unbalance must be produced in the circuit. For instance, the circuit may .be reversed from on to off status by applying a suflicient positive potential to `point .GIL which connects t0 .the grid .of triode 655B, or by applying a negative pulse to .point till?. which connects to the grid of triode |581...

Assume that the trigger circuit is in oil state.; i. e., its triode GBR is conductive while its triode GSL is at cut-oil". If a positive driving pulse of suicient amplitude is applied to point yllft, the grid bias of triode 68L will be reduced suiiiciently to allow SBL to start conducting. Current will now from line 5! via resistor 62L and the triode ESL to line 6|. The potential at point L will drop suddenly, so that a negative pulse will be fed by condenser BBL to the grid of triode "68E, The grid bias of triode .68B will increase to cut- Oif bias, and current flow in 581s will cease sub-V stantially instantaneously. PointeR will rise suddenly in potential, so that a positive pulse will feed via condenser 165B to the grid of SSL, promoting the increase in grid potential or" @8L which was initiated by the positive driving pulse applied to the point BR. Triode 53L is now conductive and triode SBR is non-conductive; i. e.,

n the trigger circuit has been reversed to on state.

To trip the circuit back to on state, a positive pulse of suicient amplitude may be applied to point BTL. The grid of SBR will `be increased in potential to start current flow through 68E. In a manner now clear, the shift to on status of the circuit will be -completed and will be self-sus-v tained. Thus, positive pulses successively applied to opposite branches of the circuit eiiect successive reversals of the circuit.

Similarly, .a Steep negative driving pulse mayrv effect reversals of the trigger circuit. In order for the negative pulse to effect the same shift of the circuit as a positive pulse, the negative pulse must 4be applied to a point of the circuit opposite the point to which a positive pulse must be applied. Thus, if the circuit is oi, it may be tripped to on state by a steep positive pulse impressed on point G1R or, alternatively, by a steep negative pulse impressed on point STL. The steep negative pulse impressed on point 6'IL will reduce the grid potential oi triode GSR to cut-off value. Point EER thereupon will rise abruptly in potential, feeding a positive pulse via condenser @R to the grid of triode GBL. The grid bias of BSL thereby will be reduced sufficiently to allow BSL to Start conducting. Point BGL will drop suddenly in potential, feeding a negative pulse to the grid of SSR, promoting the blocking of BSR which was initiated by the negative driving pulse applied to point BIL. The circuit thus may be reversed from off to on state by a steep negative pulse applied to point 67L. Similarly, the circuit may be reversed from on to oil? state by a steep negative pulse applied to point STR.

In Fig. 2, the potential changes at point iL of the trigger circuit I (Fig. l) are graphically indicated. At the start of the period of operation covered by Fig. 2, the circuit I is in on status. Hence, point SIL is then at its low potential, designated n, which is sufciently lower than cathode potential to sustain triode ESR in non conductive state. Shortly, thereafter, under control of means described later, the circuit I is tripped to 01T status. Hence, point STIL rises in potential and, eventually, in the fully triggered off status of the circuit, reaches the steady potential designated h in Fig. 2. The potential h is such as to sustain triode 69B in conductive status. Thereafter, by means described later, the circuit I is shifted back to its on status. In the initial portion of the shift, triode SSL starts to conduct and condenser BSL discharges substantially instantaneously through a circuit including triode ESL and resistor GGL, thus producing a sharp and steep drop in potential at point 61L, which is in the form of a sharp negative pulse. The amplitude of this negative pulse, as indicated in Fig. 2, exceeds the n potential value. As the condenser BEL completes its discharge, point 5l! exponentially rises in potential -to the 11, value at which it stays until the circuit is again tripped to oi status. Thus, whenever the trigger circuit is shifted from off to on status, a steep, sharp negative pulse is produced at point BIL. This negative pulse exceeds the amplitude of the positive pulses which appears at point BTL when I is turned oiT. Similarly, such a negative pulse will be produced at ETR of the trigger cir-cuit as the circuit is being turned off. Fig. 2 shows the negative pulse thus produced at point SIR of trigger circuit E.

The production of this negative pulse at either point iiL or SIR of the trigger circuit and the utilization of such 4pulse are features of the present invention. By reason of this negative pulse being of an amplitude greater than the positive pulses, discriininative or selective utilization of the pulses may be effected. Thus, point BTL of circuit I is coupled by a condenser v|85 and resistor E84 to point lL of circuit E. The condenser and resistor have such values that the positive pulse appearing at SIL of I when it is turned off, is attenuated to such extent that it is ineffective upon point ETL of E. A negative pulse of similar amplitude would also be reduced by condenser M5 and resistor |84 to ineffective value. But by producing a negative pulse at point BIL of I which exceeds the amplitude of the positive pulse which may appear at this point, effective negative potential is 'transmitted by condenser IE5 resistor ii to point 'IL of E. As represenative, circuit I was so arranged and powered that the n potential (see Fig. 2) at point BIL was approximately 30 volts and the h value was about 5G volts, so that the positive pulse had an amplitude of about 20 volts. The negative pulse was between two and three times the amplitude of the positive pulse or between i0 and 60 volts negative with respect to the h value. The condenser !25 was in the order of about 100 micromicrofarads and the resistor i3d was between .l to .2 megohin. Other values could be used which will give the required result. It is only necessary that if E is on and then I is turned oil, the positiveI pulse appearing at point STL of I shall be so reduced as it is fed through condenser S and resistor lili that it is ineiective to trip E to itsl oli status. On the other hand, if E is off and I is turned on, the steep negative pulse at point GIL of I shall be effective, by way of condenser H85 and resistor E84, to trip E to on status. In this manner, negative and positive pulses at the same point of the controlling circuit I are selectively effective upon a controlled circuit.

The means for applying driving pulses to trigger circuit I will now be described. Circuit breakers H62 and 63 (Fig. l) are mounted on a continuously rotating shaft 3i. Circuit breaker i652 has two tracks c and c wiped by brushes IBil. Circuit breaker H63 has three tracks a, b, and c wiped by similar brushes iil. Tracks e are com mon contact rings. Track a 62 has one short contact spot. Track a of lii has one short Contact spot which reaches its brush M59 after the spot on track a of MS2 has reached its brush position, and track b of E63 has a contact spot which reaches its brush position after the spot on track ci of 63 has traversed its brush position. In short, the contact spots on tracks a (62), a (H53) and b (it) successively reach brush positions.

The brush itil which wipes track c (H52) is connected by a wire 20 to the normally open side of a switch 95. The opposite, normally closed side of switch is connected to the junction of resistors 92 and 93 which are in series across plus' and minus lines 5i! and 5l. The common of the switch 95 is connected to one side of a condenser 94 which connects at the other side to line 5I. Accordingly, in the shown position of switch 95, condenser Sil will be charged to the potential across resistor 93. Upon the reversal of switch 55, condenser 9/11 is connected to wire 2i) and is ready to discharge a steep positive pulse. The pulse discharge, however, is timed by the engagement of the contact spot of track a of circuit breaker 552 with its brush 50. Upon such engagement, a positive pulse of current ilows from one side of condenser 94 via the switch 95 in reversed position. the wire 2t, the circuit breaker 62, a resistor S25, the line Sil, thence via a portion of voltage divider 55-53 to line 5i and back to the opposite side of condenser Qt. Resistor is tapped by the grid oi' a triode I26b. The resistor 125 termina-tes at line 8i! which is lower in potential than the line iii to which the cathode of triode itb connects. I-Ience, triode lZb is -normaily at negative bias and is nonconductive. When resistor 825 is positively pulsed by the `circuitJ just traced, the potential of the grid oi ltriode |261) rises above cut-off value, and an amplified lnegative pulse appears on the .anode oi the triode. rThis negative pulse is transmitted to point GSR of trigger circuit I. It may be assumed that circuit I is on at the start of the period under discussion. Hence, the negative pulse now applied to point SSR of I and fed via resistor @ESR to point 61B, brings about reversal ci circuit I from on to off state in the manner previously explained. Accordingly, point 61L of circuit I rises from its low potential n (Fig. 2) to its upper potential h. This rise in lpotential, or the 'positive pulse on point G'IL of trigger circuit I is so attenuated by condenser |85 and resistor i841 that it has no effect on point STL of trigger circuit E. Hence, circuit E which is on at this time, for reasons which will be made clear later, will not be reversed in status under control of the positive pulse at L of I.

When circuit I is oil", its point 'l'L is at the higher potential. h (Fig. 2). Point SIL of I also is `connected tothe control grid of pentode |30. As previously described, the suppressor grid of l Sil continually receives the positive pulses derived from the lower end of resistor 9 laad. Now, with the control grid raised in potential, tube |30 will respond to the positive pulses in its suppressor and will convert them to amplied negative pulses at the lower end of resistor |34, and the connected wire |213, as indicated in Fig. 2. 'Ihe negative pulses on wire t28 are communicated by a condenser l22e and resistor |2|e to point G1R of trigger circuit E. The circuit Eis on at the start of the period under discussion. Hence, the rst negative pulse derived from wire |29 and applied to point @IR of E is edective to reverse E from its on to its oi state. This reversal is attended by the appearance of the steep negative pulse at point SIR of E, as indicated in Fig. 2. This negative pulse fed by a resistor |23e and condenser .52de to a resistor ||2u. Resistor ||2u is tapped by the grid of a pentode |i3u. The screen of this pentode is maintained at suitable iixed potential by a pair of resistors Hu and Hu and a condenser' llu shunting llu. The suppressor of ||3u is connected to its cathode. Hence, 0peration of tube liu is controlled solely by its control grid. The cathode of tube ||3u and the resistor N21i both connect to line 6|, so that the tube is normally at zero grid bias and is conductive. Upon the appearance of a negative pulse on resistor Hu, the grid bias of ||3u is increased and current ow in ||3u is reduced. As a result, a positive pulse is produced on the anode or Situ and is fed by a wire 96u to an electronic accumulator order which is described in my parent application, Serial No. 515,719, filed December 27, 1943. The positive pulse received from wire Qtu'by the accumulator order effects an entry of value l in this order.

Subsequently, the circuit I is triggered Vback to its on status and, in consequence, circuit I switches the circuit E back to its on status. The return of circuit I to on status is timed by circuit breaker |53. Track a of |53 is connected via its brush it@ to the junction of a pair of resistors |8| and |82 across lines 5i) and 5|. Track c of |63 is coupled via a condenser |83 to line 5|. Track b of |63 is connected by a switch #2 IND., in the position shown, to point STR oi circuit I. When the contact spot on track a of |63 reaches brush position, a charging circuit for condenser m3 is closed from line 50 via resistor IIBI, the brush `for track a of |63, the contact spot of this track, the Acommon track c of |63, the brush for this track c, and via the condenser l|83 to line'5|. Condenser |83 is thereby charged tothe potential across resistor |82. Thereafter, the contact spot on track a of |63 leaves the related brush |59 and the contact spot on track b of |63 reaches the brush |6ii for track b. A discharge circuit for condenser |83 is thereby established, and the condenser discharges a positive pulse via common track c of |63, the spot on track b, and the switch #2 IND., upon point tlR of circuit I. This positive pulse is of sufficient forceto bring about the triggering o circuit I from its oir to its on status. As circuit I reverses to its on status, a steep negative pulse appears at lits point SIL, as previously described. This negative pulse is transmitted by condenser `85 and resistor |84 to point VGTL of circuit E, turning on E in the manner previously explained.

To summarize, circuits I and E are initially in on state. Upon reversal of switch S5, I is turned orf under control of circuit breaker |62. This renders tube i3!) effective to produce negative pulses on wire |29. The iirst pulse on Wire |20 turns o circuit E. As circuit E turns off, a steep negative pulse appears at its point 151B. This pulse is converted by tube |3u into an entry pulse on wire 96u for an accumulator order. Subsequently, I is turned on under control of circuit n breaker |63. Accordingly, a steep negative pulse is produced at point tlL of I. This pulse is fed to point @7L of circuit E and turns Exon again.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intenion, therefore, to "be limited only as indicated by the scope of the following claims.

What is claimed is:

l. The combination with a controlled circuit capable of responding to positive and negative pulses of adequate amplitude; of an electronic trigger circuit having two alternative stable states and comprising a pair of parallel, resistive, voltage dividers adapted to be energized from a source of voltage, rst and second electronic tubes corresponding to the rst and second of said dividers respectively, each of said .tubes having an anode and a cathode connected in parallel circuit relation with a portion of the corresponding divider and also having a grid, the anode of .each tube being connected to a iirst intermediate point on the corresponding divider and the grid being connected to a second intermediate point on said portion of the other divider, and first and second condensers corresponding to said first and second dividers, respectively, each condenser being connected between the rst and second points on the corresponding divider, the first tube being conductive and the second tube being non-conductive in one of said stable states of the trigger circuit with the conductive status of the tubes being reversed in the opposite stable state, whereby the grid of the rst tube is at a higher voltage level in said one stable state than in said opposite stable state, said trigger circuit being switchable from either stable state to the other upon an ap-k plication thereto of an unbalancing potential, whence upon the trigger circuit being switched to said one state a positive voltage vpulse appears at the grid of the rst tube and upon being switched to said opposite state a negative voltage pulse appears at that grid, the condenser connected between the rst and second points on the second divider being charged while the second tube is non conductive and thereafter discharged through the second tube and a part of said portion of the second divider when the second tube becomes conductive upon the trigger circuit being switched to said opposite state, to cause the negative pulse at the grid of the rst tube to exceed the positive pulse in amplitude; and pulseattenuating reactance means coupling the grid of the rst tube to the controlled circuit for transmitting pulses appearing at said grid of the first tube to the controlled circuit while attenuating such pulses to an extent that the positive pulse is inadequate to operate the controlled circuit while the negative pulse of greater amplitude is adequate.

2. The combination with a controlled trigger circuit having two alternative stable states, which controlled circuit is capable of being switched from one stable state to the other upon application of a positive voltage pulse of adequate amplitude to a portion of the circuit and of being switched back to said one state upon application to the same portion of a negative voltage pulse of adequate amplitude; of an electronic controlling trigger circuit having two alternative stable states and comprising a pair of parallel resistive voltage dividers adapted to be energized from a source of voltage, iirst and second electronic tubes corresponding to the first and second of said dividers respectively, each of said tubes having an anode and a cathode connected in parallel circuit relation with a portion of the corresponding divider and also having a grid, the anode of each tube being connected to an intermediate point on the corresponding divider, means including a part of said portion of the iirst divider and a ilrst condenser shunting said part for coupling the anode of the rst tube to the grid of the second tube, and means including a part of said portion of the second divider and a second condenser shunting said part for coupling the anode of the second tube to the grid of the iirst tube, the iirst tube being conductive and the second tube being non-conductive in one of said stable states of the trigger circuit with the conductive status of the tubes being reversed in the opposite stable 10 state, whereby the grid of the first tube is at a higher voltage level in said one stable state than `in said opposite stable state, said trigger circuit being switchable from either stable state to the other upon an application thereto of an unbalancng potential, whence upon the trigger circuit being switched to said one state a positive voltage pulse appears at the grid of the iirst tube and upon being switched to said opposite state a negative voltage pulse appears at that grid, the second condenser being charged while the second tube is non-conductive and thereafter discharged through the second tube and another part of said portion of the second divider when the second tube becomes conductive upon the trigger circuit being switched to said opposite state to cause the negative pulse at the grid of the rst tube to exceed the positive pulse in amplitude; and condenser-resistor means coupling the grid of the first tube to the controlled circuit for transmitting pulses appearing at the grid of the first tube to the controlled circuit while attenuating such pulses to an extent that the positive pulse is inadequate to operate the -controlled circuit while the negative pulse of greater amplitude is adequate.

ARTHUR H. DICKINSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,266,401 Reeves Dec. 16, 1941 2,266,526 White Dec. 16, 1941 2,272,070 Reeves Feb. 3, 1942 2,338,395 Bartelink Jan. 4, 1944 2,373,145 Sensiper et al Apr. 10, 1945 2,402,916 Schroeder June 25, 1946 OTHER REFERENCES Trigger Circuits, Electronics, Aug. 1939 (250- 27 TR), pages 14-17.)

A Four-Tube Counter Decade, Electronics (250-27 TR), pages 110-113, 358 and 360, June 1944.

A.I.E.E. Technical Paper -119, June 1940-A Wide-Band Square- Wave Generator, by Bartelink. Copy in 250-36-13.2. 

